如何計算值的差在一列

Question

C1 |C2 |C3 
a |b1 |1 
a |b2 |2 
a |b3 |3 
a |b4 |4 
b |b1 |5 
b |b2 |6 
b |b3 |10 
b |b4 |11 

鑑於上述表中的數據，我想輸出象下面這樣：

C1 |DIFF 
a |3 
b |6 

這裏，DIFF是C3列值，其中C2='b4'和C2='b1'的差。 在Oracle中執行它的邏輯是什麼？

Answer 1

也許這...... my_table是你的輸入表。

select t1.c1 as c1, t1.c3 - t2.c3 as diff 
from (select c1, c3 from my_table where c2 = 'b4') t1 
     inner join 
     (select c1, c3 from my_table where c2 = 'b1') t2 
     on t1.c1 = t2.c1 
;